The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Pumping of process fluids are used in many industries Process fluids may be pumped with a various types of pumps that are driven by a drive fluid. A slurry is one type of process fluid. Slurries are typically abrasive in nature. Slurry pumps are used in many industries to provide the slurry into the process. Sand injection for hydraulic fracturing (fracking), high pressure coal slurry pipelines, mining, mineral processing, aggregate processing, and power generation all use slurry pumps. All of these industries are extremely cost competitive. A slurry pump must be reliable and durable to reduce the amount of down time for the various processes.
Slurry pumps are subject to severe wear because of the abrasive nature of the slurry. Typically, slurry pumps display poor reliability, and therefore must be repaired or replaced often. This increases the overall process costs. It is desirable to reduce the overall process costs and increase the reliability of a slurry pump.
Direct acting liquid driven pumps have been developed, in which a high pressure drive fluid is used to pressurize a process fluid by direct contact, or separated by a membrane or piston. The known system described below is used for a slurry as the process fluid.
Hydraulic fracturing of gas and oil bearing formations requires high pressures typically up to 15,000 psi (103421 kPa) with flow rates up to 500 gallons per minute (1892 liters per minute). The total flow rate using multiple pumps may exceed 5,000 gallons per minute (18927 liters per minute).
Various types of pressure intensifiers use moderate pressure drive fluid to pressurize a high pressure process fluid using several pistons or plungers. The drive fluid is often clean water or hydraulic oil and the pumpage is the process fluid, such as slurry.
Referring now to FIG. 1, a slurry pressure amplifier system 10 is illustrated. The system 10 includes a cylinder 12 that has a piston 14 that moves back and forth within the cylinder 12. The cylinder 12 has a longitudinal axis 16. The piston 14 moves in an axial direction. The piston 14 may be coaxial with the cylinder 12. Although the piston 14 and the cylinder 12 are cylindrically shaped, various shapes may be used.
The piston 14 may include a plurality of sealing rings 18 disposed on an edge of the piston 14, the piston 14 divides the cylinder 12 into a first volume 20 and a second volume 22. The sealing rings 18 prevent fluid leakage from between the first volume 20 and the second volume 22 within the cylinder 12. A first port 24 communicates drive fluid into or out of the cylinder 12 at the first volume 20. A second port 26 communicates drive fluid into and out of the second volume 22 within the cylinder 12. The drive fluid may be water or another type of hydraulic fluid.
The cylinder 12 has a cylindrical wall 30, a first end wall 32 and a second end wall 34. That defines the volume of the cylinder. The first end wall 32 has a first opening 36. The second end wall 34 has a second opening 38 therethrough.
The end wall 32 of the cylinder 12 has a seal 40 and a first pump barrel 42 coupled thereto. The seal 40 may be referred to as packing. The second end wall 34 has a seal 44 and a second pump barrel 46 coupled thereto.
The piston 14 has a first plunger 50 that is received within the first opening 36 and the seal 40 and extends into the first pump barrel 42. The second opening 38 in the second end wall 34 receives a second plunger 52. The second plunger 52 extends from the piston 14 through the opening 38, the seal 44 and into the second pump barrel 46. As the piston 14 moves in the axial direction, the plungers 50, 52 move within the respective barrels 42, 46.
The barrels 42, 46 alternatively receive pumpage and pressurize the pumpage. The first pump barrel 42 is in fluid communication with a first check valve 60 and second check valve 62. The barrel 46 is in fluid communication with a third check valve 64 and a fourth check valve 66. The check valves 60, 64 communicate fluid into the respective barrels 42, 46. The check valves 62, 66 communicate fluid out of the respective barrels 42, 46. A low pressure manifold 70 communicates low pressure pumpage such as slurry to the first check valve 60 and the second check valve 64. High pressure pumpage pressurized within the barrels 42, 46 is communicated from the check valves 62 and 66 to a high pressure manifold 72. The high pressure manifold 72 is in communication with a process such as a well head for use and a use in fracking or other suitable use. The low pressure pumpage within the low pressure manifold 70 is increased in pressure due to the pumping action of the plungers 50, 52 and the movement of the piston 14 which acts to increase the pressure of the pumpage as will be described in detail below.
A drive fluid is communicated to the first volume 20 through port 24 and to volume 22 through port 26. The port 24 is in communication with a pipe 74. Port 26 is in communication with a pipe 76. The pipes 74 and 76 are in fluid communication with a plurality of valves. The plurality of valves may be disposed within a single spool valve 80. The spool valve 80 is linearly actuated by a linear actuator 82 that is in communication with the spool valve 80 with a rod 84. The spool valve 80 has a plurality of ports which include a first port 86 and a second port 88. The ports 86 and 88 may act as an inlet and an outlet to the spool valve 80. A plurality of ports 89, 90 and 92 may also be part of the spool valve 80. Ports 89 and 92 are in communication with a hydraulic tank 94. Port 90 is in communication with a high pressure pump 96. Pipes in the form of a manifold 98 may form the interconnections between the ports 89-92 and the tank 94. Pipes 100 and 102 couple the tank 94 to the high pressure pump 96 and the high pressure pump 96 to the port 90, respectively.
The rod 84 is used to move valve disks 110 and 112. The valve disks 110, 112 are illustrated in the rightmost position. In this position, the high pressure pump 96 communicates high pressure drive fluid to the port 90 through the pipe 102. Fluid is communicated through the port 90 to the port 88 through the spool valve 80. The drive fluid is communicated to the port 26 and the first volume 22 of the cylinder 12. The high pressure fluid communicated to the first volume 22 pushes the piston 14 within the cylinder 12 to the left as compared to the drawing in FIG. 1. The first volume 20 is being reduced and communicated from the port 24 through the pipe 74 to the port 86 of the spool valve 80. The low pressure fluid is communicated from port 86 to port 89 through the spool valve 80. The fluid is communicated through the manifold 98 to the tank 94 where it may be reused by the high pressure pump 96.
In a second state of operation of the spool valve 80 (not illustrated), the plurality of valves within the spool valve 80 operate as follows. The rod 84 moves the valve disks 110, 112 to the left. Disk 110 is then between port 89 and port 86. Disk 112 is then positioned between port 90 and port 88. In this manner, high pressure fluid from the high pressure pump 96 is communicated to port 24 and the first volume 20 through the port 86 of the spool valve and pipe 74. Low pressure fluid is returned to the tank 94 from the second volume 22 through port 26, pipe 76, port 88, port 92 and the manifold 98 of the spool valve.
By switching the spool valve 80 between the two states as described above, the fluid pressure drives the piston 14 in an oscillating motion that results in the movement of the plungers 50, 52 into and out of the pump barrels 42, 46, respectively. As the respective plunger 50, 52 withdraws from the respective barrel 42, 46, the appropriate check valve 60 or 64 opens to admit low pressure pumpage, such as slurry, into the barrel. When the direction of the plunger 50, 52 is reversed, the check valves 60, 64 close and the pumpage is pressurized to a high pressure. The high pressure pumpage is communicated to the high pressure manifold 72 through check valves 62 and 66.
To summarize, when high pressure drive fluid is communicated to the second volume 22, fluid is being removed from the first volume 20. The piston 14 moves in a leftward position relative to FIG. 1 and thus the plunger 50 extends into the pump barrel 42 forcing a high pressure pumpage from the check valve 62 into the high pressure pumpage manifold 72. At the same time, the plunger 52 is withdrawing from the pump barrel 46 drawing low pressure pumpage into the barrel 46 through the check valve 64. In the reverse direction, when high pressure drive fluid is communicated to the first volume 20 and low pressure drive fluid is being moved from the second volume 22, the plunger 50 is being withdrawn into the pump barrel 42. This draws in low pressure pumpage through the check valve 60 and closed the check valve 64. At the same time, the pump barrel 42 is pressurizing pumpage by the action of the plunger 52 which is moving in a rightward direction relative to FIG. 1. The check valve 62 is in a closed position while the check valve 66 is in an open position and communicating high pressure pumpage to the high pressure pumpage manifold 72.